Ventilation of oxygen to oxygen minimum zone due to anticyclonic eddies in the Bay of Bengal
"Intense oxygen minimum zone (OMZ) occurs in the mid‐depth of the Eastern Tropical Pacific (ETP), Arabian Sea (AS), and Bay of Bengal (BoB). However, the occurrence of anammox/denitrification was reported only in the ETP and AS and its absence in the BoB is attributed to presence of traces of dissolved oxygen (DO). Anticyclonic Eddies (ACE) supply high nutrient, organic‐rich and oxygen poor waters from the coastal upwelling regions leading to strengthening of OMZ in the offshore of AS and ETP. [...]"
Authors: V. V. S. S. Sarma, T. V. S. Udaya Bhaskar
Hazards of decreasing marine oxygen: the near-term and millennial-scale benefits of meeting the Paris climate targets
"Ocean deoxygenation is recognized as key ecosystem stressor of the future ocean and associated climate-related ocean risks are relevant for current policy decisions. In particular, benefits of reaching the ambitious 1.5 °C warming target mentioned by the Paris Agreement compared to higher temperature targets are of high interest. Here, we model oceanic oxygen, warming and their compound hazard in terms of metabolic conditions on multi-millennial timescales for a range of equilibrium temperature targets. [...]"
Source: Earth System Dynamics
Authors: Gianna Battaglia and Fortunat Joos
Drivers and mechanisms of ocean deoxygenation
"Direct observations indicate that the global ocean oxygen inventory is decreasing. Climate models consistently confirm this decline and predict continuing and accelerating ocean deoxygenation. However, current models (1) do not reproduce observed patterns for oxygen changes in the ocean’s thermocline; (2) underestimate the temporal variability of oxygen concentrations and air–sea fluxes inferred from time-series observations; and (3) generally simulate only about half the oceanic oxygen loss inferred from observations. [...]"
Source: Nature Geoscience
Authors: Andreas Oschlies et al.
Enhanced carbon-sulfur cycling in the sediments of Arabian Sea oxygen minimum zone center
"Biogeochemistry of oxygen minimum zone (OMZ) sediments, which are characterized by high input of labile organic matter, have crucial bearings on the benthic biota, gas and metal fluxes across the sediment-water interface, and carbon-sulfur cycling. Here we couple pore-fluid chemistry and comprehensive microbial diversity data to reveal the sedimentary carbon-sulfur cycle across a water-depth transect covering the entire thickness of eastern Arabian Sea OMZ, off the west coast of India. [...]"
Source: Scientific Reports
Authors: Svetlana Fernandes et al.
Gulf of Mexico 'dead zone' forecasted to exceed the size of Connecticut
"Scientists have predicted the dead zone, or area with little to no oxygen in the northern Gulf of Mexico, will become larger than the state of Connecticut by the end of July. The dead zone will cover about 6,620 square miles of the bottom of the continental shelf off Louisiana and Texas. While there are more than 500 dead zones around the world, the northern Gulf of Mexico dead zone is the second largest human-caused coastal hypoxic area in the world."
Marine redox fluctuation as a potential trigger for the Cambrian explosion
The diversification of metazoans during the latest Neoproterozoic and early Cambrian has been attributed to, among other factors, a progressive rise in surface oxygen levels. However, recent results have also questioned the idea of a prominent rise in atmospheric oxygen levels or a major or unidirectional shift in the marine redox landscape across this interval. Here, we present new carbonate-associated uranium isotope data from upper Ediacaran to lower Cambrian marine carbonate successions. [...]"
Authors: Guang-Yi Wei et al.
Climate and marine biogeochemistry during the Holocene from transient model simulations
"Climate and marine biogeochemistry changes over the Holocene are investigated based on transient global climate and biogeochemistry model simulations over the last 9500 years. The simulations are forced by accelerated and non-accelerated orbital parameters, respectively, and atmospheric pCO2, CH4, and N2O. The analysis focusses on key climatic parameters of relevance to the marine biogeochemistry, and on the physical and biogeochemical processes that drive atmosphere–ocean carbon fluxes and changes in the oxygen minimum zones (OMZs). [...]"
Authors: Joachim Segschneider, Birgit Schneider, and Vyacheslav Khon
Dissolved Organic Matter Influences N2 Fixation in the New Caledonian Lagoon (Western Tropical South Pacific)
"Specialized prokaryotes performing biological dinitrogen (N2) fixation (“diazotrophs”) provide an important source of fixed nitrogen in oligotrophic marine ecosystems such as tropical and subtropical oceans. In these waters, cyanobacterial photosynthetic diazotrophs are well known to be abundant and active, yet the role and contribution of non-cyanobacterial diazotrophs are currently unclear. The latter are not photosynthetic (here called “heterotrophic”) and hence require external sources of organic matter to sustain N2 fixation. [...]"
Source: Frontiers in Marine Science
Authors: Mar Benavides et al.
Oxygen Pathways and Budget for the Eastern South Pacific Oxygen Minimum Zone
"Ventilation of the eastern South Pacific Oxygen Minimum Zone (ESP‐OMZ) is quantified using climatological Argo and dissolved oxygen data, combined with reanalysis wind stress data. We (1) estimate all oxygen fluxes (advection and turbulent diffusion) ventilating this OMZ, (2) quantify for the first time the oxygen contribution from the subtropical versus the traditionally studied tropical‐equatorial pathway, and (3) derive a refined annual‐mean oxygen budget for the ESP‐OMZ. In the upper OMZ layer, net oxygen supply is dominated by tropical‐equatorial advection, with more than one‐third of this supply upwelling into the Ekman layer through previously unevaluated vertical advection, within the overturning component of the regional Subtropical Cell (STC). [...]"
Authors: P. J. Llanillo et al.
Upper ocean hydrology of the Northern Humboldt Current System at seasonal, interannual and interdecadal scales
"Since the 1960’s, the Instituto del Mar del Perú (IMARPE) collected tens of thousands of in-situ temperature and salinity profiles in the Northern Humboldt Current System (NHCS). In this study, we blend this unique database with the historical in-situ profiles available from the World Ocean Database for the period 1960-2014 and apply a four-dimensional interpolation scheme to construct a seasonal climatology of temperature and salinity of the NHCS [...]"
Source: Progress in Oceanography
Authors: Carmen Grados et al.